This invention relates to the use of reaction products of ethylenically-unsaturated dicarboxylic acids or their anhydrides, and dicarboxylic acid neutral esters with unsaturated fatty alcohols as adjuvants or assistants for the preparation of pigment pastes with a high content of pigment.
In the content of the present invention, pigment pastes are understood to be suspensions of pigments and fillers, mainly of inorganic nature, in organic liquids that are nonvolatile or difficult to volatilize.
The mixing of powdered pigments into plastics, coating materials and printing dyes poses problems with respect to the homogenizing of the pigments as well as their handling during the operation. For example, the transporting, dosing and dust-free handling of powdered pigments are highly problematical during the continuous production of colored plastics.
Pigment pastes prepared from liquid, organic media and powdered pigments are finding increasing application to eliminate these difficulties.
Suitable for the pigment pastes are pigments such as titanium dioxide types, with or without secondary treatment, natural and synthetic iron oxide pigments, chromium yellow, chromic oxide green, and molybdate red. Furthermore, powdered fillers such as silicon dioxide, calcium carbonate and dolomite can also be incorporated into the pigment paste. Suitable as the substantially non-volatile liquid organic media are among others, dioctyl phthalate, dibutyl phthalate, esters of maleic acid, esters of fatty acids, mineral oils, natural oils and their epoxidation products. The pastes are prepared with the aid of conventional mixers such as agitators, kneading machines, rolling mills or fast mixing aggregates of the dissolver type.
The pastes prepared in this manner have the disadvantage that their content of pigment is small, when the goal is a liquid preparation that is easy to measure out. For the practical application, however, it usually is necessary and economical, for example, for the coloring of plastics, to keep the liquid part of the pigment pastes as low as possible. The demand for pigment pastes with high pigment contents arises from these requirements.
Various adjuvants or assistants have been suggested that, in the form of relatively small additions, are expected to reduce the viscosity of pigment pastes and thus permit the preparation of pastes with higher pigment contents. For example, technical grade glyceryl monooleate frequently is used in actual practice. Such products, however, meet the set requirements only partially.